CN106771828B - Detection device and method for powered device of Ethernet power supply system - Google Patents
Detection device and method for powered device of Ethernet power supply system Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/66—Testing of connections, e.g. of plugs or non-disconnectable joints
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F1/00—Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
- G06F1/26—Power supply means, e.g. regulation thereof
- G06F1/266—Arrangements to supply power to external peripherals either directly from the computer or under computer control, e.g. supply of power through the communication port, computer controlled power-strips
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F1/00—Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
- G06F1/26—Power supply means, e.g. regulation thereof
- G06F1/28—Supervision thereof, e.g. detecting power-supply failure by out of limits supervision
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F1/00—Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
- G06F1/26—Power supply means, e.g. regulation thereof
- G06F1/32—Means for saving power
- G06F1/3203—Power management, i.e. event-based initiation of a power-saving mode
- G06F1/3206—Monitoring of events, devices or parameters that trigger a change in power modality
- G06F1/3209—Monitoring remote activity, e.g. over telephone lines or network connections
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/02—Details
- H04L12/10—Current supply arrangements
Abstract
A powered device detection device of a power over Ethernet system is used for detecting whether a device connected to the power over Ethernet system is suitable for power supply. The detection device is configured to: a detection signal may be applied to the device and a response signal of the device may be measured. The detection signal comprises a first voltage, a second voltage, a third voltage and a fourth voltage in sequence; the first voltage and the third voltage have substantially the same value, and the second voltage and the fourth voltage have substantially the same value. The application time of the fourth voltage is the sum of the application time and the extension time of the second voltage. The detection means determines that the device is not suitable for supplying power when the response signal is outside a predetermined range. The invention also provides a method of performing the detection.
Description
Technical Field
The invention provides a circuit and a method for detecting a POE (Power over Ethernet) standard-compliant powered device in a power over Ethernet system.
Background
The Power Over Ethernet System-POE System (Power Over Ethernet System) has been a popular application. IEEE has issued two POE standards, IEEE 802.3af and IEEE 802.3at (hereinafter referred to as "POE standards for IEEE" or "POE standards"), in 2003 and 2009, respectively, and is widely adopted in various fields. The POE technology enables devices such as network phones, wireless base stations, network cameras, hubs, and even computers to be powered by ethernet without the use of additional power supplies and outlets. This technique of combining data transfer and power supply significantly reduces the overall network computer system cost and complexity.
In a Power over ethernet system, electrical Power is supplied to a Powered Device (PD) by a Power Source Equipment (PSE) via a data cable of the ethernet network. Suitable power supply devices include ethernet switches, routers, other network switching devices, and midspan devices in data communications networks. In such a system, a powered device refers to a device connected to a network and configured to draw power from the network or request power from the power source equipment.
In a power over ethernet system, a power source apparatus is connected to a plurality of powered devices via a network connection port, and also to a plurality of devices that cannot or cannot take power from the power source apparatus. In application, the powered device includes a device conforming to the POE standard of the IEEE described above, and a device compatible with the standard. The IEEE POE standard provides that before the power supply equipment provides power to a specific device, the device must be detected to determine whether the device is a powered device meeting the POE standard. However, most power supply equipment or product suppliers including the power supply equipment may also configure the power supply equipment to simultaneously detect the powered Device and determine whether the Device is a POE compliant Device, such as a Legacy Device (Legacy Device). If the detection result is yes, power is also supplied to the compatible device.
According to the IEEE POE standard, the power supply apparatus applies a signal to the connection port to which the device under test is connected, and then detects a response signal of the device under test from the connection port, when the detection is performed. And if the response signal shows a Signature Resistance (Signature Resistance) ranging from 19 to 26.5 kilo ohms, judging that the device to be tested is a power receiving device conforming to the IEEE standard. The POE standard also specifies that the voltage of the signal emitted by the power supply device should be approximately between 2.8V and 10V, and the current should be approximately less than 5 mA. The voltage of the test signal should have a difference of more than 1V.
When performing the detection, typically, the power supply apparatus applies a voltage or a current to a specific connection port, and detects a response signal of the device under test after a predetermined time. The signature resistance is calculated from the current/voltage relationship between the two signals. If a current is applied, the current is typically in the range of 150 μ A to 400 μ A. And measuring the voltage of the connection port to calculate the value of the signature resistance. In this case, the device under test conforming to the POE standard will cause the voltage measured at the connection port of the power supply equipment to drop by about 2.8V to 10V.
Conversely, if the detection signal is a voltage, the voltage is typically in the range of about 2.8V to 10V. The current measured at the port is between about 87.5 μ A and 625 μ A.
Based on the detection result, it is determined whether to perform the next operation to "classify" the power receiving device. And different power is supplied to the power receiving device according to the classification result.
US patent specification US 7856561 discloses an apparatus for detecting legacy devices in a power over ethernet system. The test signals sequentially applied by the power supply equipment of the device to a specific network connection port comprise two current values I1 and I2, and the voltages V1 and V2 of the connection port are measured after 160ms respectively. According to the ratio of the two voltage difference values and the current difference value, whether the device connected to the port is a powered device is judged, whether the device is classified is determined, and whether the device is a standard powered device or a compatible device is judged. In detail, the apparatus calculates the value of Rdet ═ V1-V2)/(I1-I2. If the Rdet value is within a certain range, the device is judged to be a power receiving device meeting the standard. If the value of Rdet is less than a predetermined value or is a negative value, the device is determined to be an old device. If none of the above conditions are met, it is determined that the device is neither a compliant nor an old device.
Chinese patent publication No. CN101031861 discloses a classification of powered devices in a wired data telecommunication network. The patent applies a plurality of cycles of detection signals to the powered device to generate a plurality of sets of classification results. And (5) corresponding the classification result with the codes in the index table, and taking the obtained codes as classification codes.
In addition to the voltage range of the dut, the POE standard of IEEE also specifies that the capacitance on the powered device must be 0.15 uF. And that if the capacitance exceeds 10uF, power supply must be denied. Under such regulations, the power supply equipment provided by the manufacturers also needs to detect the device capacitance connected to the connection port to determine whether the device is a power receiving device for supplying power.
US invention patent US 8412961 discloses a circuit and method for detecting legacy devices in a power over ethernet system. The invention can judge whether the device connected to the specific connection port is a power receiving device in accordance with the IEEE standard or an old device or not, and can also judge whether the device is a simple capacitive load or a simple resistive load. The invention adopts three levels of voltage or current as detection signals. And detecting the device under test according to the current or voltage response measured at the connection port. In this invention, the three levels are substantially two levels, wherein the first level is the same as the third level. That is, while the voltage or current of the third level is applied, the same measurement as that of the first level is repeatedly applied.
This patent provides the ability to detect the capacitance of a device under test. However, the capacitance is more complicated to calculate and requires the use of CPU resources. In addition, when the capacitance exceeds the range defined by the POE standard of IEEE, the measurement result is erroneous because the charging and discharging time is long and cannot be stabilized before the measurement time. According to the specification of the patent, the detection device of the power receiving device needs to sample for a plurality of times to obtain the current/voltage signal representing the steady state.
In the prior art power over ethernet system, the detection of the powered device is limited by the variety of devices that may be connected to the connection port, which is difficult to predict in advance. And the connected devices have different characteristics, which often affect the detection accuracy. For example, the resistance and capacitance characteristics of the dut often affect the response of the dut to the detection signal, especially the time for the response signal to stabilize. Resulting in incorrect values of the sampled voltage/current signals at the time of detection.
In addition, there is no simple method for detecting the capacitance of the dut. Although the capacitance and resistance of the dut can be detected separately, whether a specific device is suitable for receiving power from the power source equipment depends on the combination of the capacitance and resistance, and even the capacitance and resistance still need to be determined through complicated procedures.
Disclosure of Invention
The object of the present invention is to provide a novel power receiving device detection device for a power over ethernet system, which can improve the correctness of the power receiving device.
It is also an object of the present invention to provide a novel power receiving device detection apparatus for a power over ethernet system, which can shorten the overall detection time of the power receiving device.
It is also an object of the present invention to provide a powered device detection apparatus for a power over ethernet system, which can correctly exclude non-powered devices to avoid unnecessary detection.
The present invention also provides a method for detecting a powered device in a power over ethernet system having the above advantages.
The invention discloses a detection device of a power receiving device of an Ethernet power supply system, which is arranged in power supply equipment of the Ethernet power supply system. The power supply equipment provides at least one communication port, and the communication port can be used for connecting the power receiving device through a network cable. The detection device is connected to the communication port and configured to apply a detection voltage signal to the communication port, wherein the detection voltage signal comprises a first voltage V1, a second voltage V2, a third voltage V3 and a fourth voltage V4 in sequence. The first voltage and the third voltage have substantially the same value, and the second voltage and the fourth voltage have substantially the same value. The application time of the fourth voltage is the sum of the application time and the extension time of the second voltage. The extension time is 0.2 to 1.5 times, preferably 0.5 to 1.0 times the second voltage application time.
The detection device is further configured to:
a first current value I1 measured from the communication port a predetermined time after the first voltage is applied, a second current value I2 measured from the communication port a predetermined time after the second voltage is applied, a third current value I3 measured from the communication port a predetermined time after the third voltage is applied, and a fourth current value I4 measured from the communication port a predetermined time after the fourth voltage is applied;
values were calculated for Rdet1 ═ V1-V2)/(I1-I2) and Rdet2 ═ V3-V4)/(I3-I4,
when one of the current values I1, I2, I3 and I4 exceeds a first predetermined value range, determining that the communication port is not connected with a power receiving device suitable for power supply;
when the delta Rdet is larger than a second preset value Rdet1-Rdet2, judging that the communication port is not connected with a power receiving device suitable for power supply; otherwise, the communication port is judged to be connected with the power receiving device suitable for power supply.
The power receiving device detection method of the power over ethernet system of the present invention includes a method performed in a power supply apparatus of the power over ethernet system. The power supply equipment is provided with at least one communication port and a detection device, wherein the communication port can be connected with a power receiving device through a network cable, and the detection device is connected with the communication port. The method is used for detecting the characteristics of the powered device connected to the communication port and comprises the following steps:
applying a detection voltage signal to the communication port, wherein the detection voltage signal sequentially comprises a first voltage V1, a second voltage V2, a third voltage V3 and a fourth voltage V4;
the first voltage and the third voltage have substantially the same value, and the second voltage and the fourth voltage have substantially the same value. The application time of the fourth voltage is the sum of the application time and the extension time of the second voltage; the extension time is 0.2 to 1.5 times, preferably 0.5 to 1.0 times the second voltage application time;
a first current value I1 measured from the communication port a predetermined time after the first voltage is applied, a second current value I2 measured from the communication port a predetermined time after the second voltage is applied, a third current value I3 measured from the communication port a predetermined time after the third voltage is applied, and a fourth current value I4 measured from the communication port a predetermined time after the fourth voltage is applied;
values were calculated for Rdet1 ═ V1-V2)/(I1-I2) and Rdet2 ═ V3-V4)/(I3-I4,
when one of the current values I1, I2, I3 and I4 exceeds a first predetermined value range, determining that the communication port is not connected with a power receiving device suitable for power supply;
when the delta Rdet is larger than a second preset value Rdet1-Rdet2, judging that the communication port is not connected with a power receiving device suitable for power supply; otherwise, the communication port is judged to be connected with the power receiving device suitable for power supply.
The above and other objects and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
Drawings
Fig. 1 is a block diagram showing a power receiving device detection device of a power over ethernet system according to an embodiment of the present invention.
Fig. 2 is a voltage-time and current-time comparison diagram showing the relationship between the detection voltage signal applied to the connection port and the response signal detected from the connection port according to the detection of the powered device of the power over ethernet system of the present invention when the device connected to the connection port is a standard or compatible powered device in the power over ethernet system.
Fig. 3 is another voltage-time and current-time comparison graph showing the relationship between the detection voltage signal applied to the connection port and the response signal detected from the connection port by the detection method of fig. 2 when the device connected to the connection port is a device unsuitable for power supply in the power over ethernet system.
Fig. 4 is another voltage-time and current-time comparison diagram showing the relationship between the detection voltage signal applied to the connection port and the response signal detected from the connection port by the detection method of fig. 2 when the device connected to the connection port is another device unsuitable for power supply in the power over ethernet system.
Fig. 5 is another voltage-time and current-time comparison diagram showing the relationship between the detection voltage signal applied to the connection port and the response signal detected from the connection port by the detection method of fig. 2 when the device connected to the connection port is another device unsuitable for power supply in the power over ethernet system.
Fig. 6 is a flowchart illustrating a power receiving device detection method of a power over ethernet system according to an embodiment of the present invention.
[ notation ] to show
10: a detection device; 11. 12, 13, 14: a connection port; 11A, 12A, 13A, 14A: a signal line; 15: a detection arithmetic unit; 16: a voltage supply; 17: a current detector; 21. 22, 23: an external device; 21A, 22A, 23A: a network cable; 100: a power supply device; 200: a power source; 201: a power line; 101: an input/output interface; v1: a first voltage; v2: a second voltage; v3: a third voltage; v4: a fourth voltage; i1: a first current value; i2: a second current value; i3: a third current value; i4: the fourth current value.
Detailed Description
The invention provides a novel device and a method for detecting a power receiving device of an Ethernet power supply system, which can detect whether the device connected to power equipment of the Ethernet power supply system is the power receiving device meeting POE standards or the device unsuitable for power supply through a single detection step, and can eliminate the device unsuitable for power supply so as to reduce unnecessary repeated detection. The detection device and the detection method can simultaneously detect the voltage and the capacitance characteristics of the device to be detected, and achieve correct results.
Fig. 1 is a block diagram showing a power-supplied device detection apparatus of a power over ethernet system according to an embodiment of the present invention. As shown in the drawing, the power receiving device detection apparatus 10 of the power over ethernet system of the present invention is provided in the power supply apparatus 100 of the power over ethernet system. The power supply equipment 100 and the power supply 200 together form the power over ethernet system, and the power supply equipment 100 has a function of transferring power transmitted from the power supply 200 via the power line 201 to a power receiving device. As shown in fig. 1, the electric power supplied from the power supply 200 enters the input/output interface 101 of the power supply apparatus 100 via the power supply line 201, and enters the detection device 10. The power supply apparatus 100 also provides a plurality of connection ports 11, 12, 13, 14 for external devices 21, 22, 23 to connect via network cables 21A, 22A, 23A. Although 4 ports are shown, it is understood by those skilled in the art that the number of ports is not limited in any way. Typically, the power device 100 may provide 8 ports, but may be higher or lower than this. There are shown 3 external devices 21, 22, 23 connected to the ports 11, 12, 14. The connection port 13 is not connected to an external device. The external devices 21, 22, 23 may be power receiving devices conforming to the POE standard of IEEE, power receiving devices compatible with the standard, power receiving devices incompatible with the standard, or even just general capacitive or resistive loads.
The power supply apparatus 100 is connected to the connection ports 11, 12, 13, 14 via 4 sets of signal lines 11A, 12A, 13A, 14A. The power supply apparatus 100 functions as a device that transfers power supplied from the power supply 200 to the external devices 21, 22, and 23 and receives power supply.
Generally, the signal lines 11A, 12A, 13A, 14A each include 2 pairs of signal lines. For transmitting electrical signals and electrical power. Meanwhile, each of the network lines 21A, 22A, and 23A also includes 2 pairs of signal lines, forming a twisted pair. Of course, the number of signal lines included in the signal line and the mesh line is not limited to any technical limit. But each group needs to include at least one pair of signal lines.
The power over ethernet system having the above structure is well known in the art and is described in various technical documents, including the above-mentioned industry standards such as IEEE 802.3af and IEEE 802.3 at. The details of which need not be described herein.
According to the POE standard of IEEE, the power supply apparatus 100 conforming to the standard must detect and classify the external devices 21, 22, and 23 to be supplied with power, before supplying power to the appropriate kinds of external devices. For a powered device that already conforms to the POE standard of IEEE or is compatible with the standard, various applicable detection and classification methods and devices have been proposed in the industry. Such as those described in the aforementioned patent documents US 7856561 and US 8412961. However, there is still no easy way to correctly detect devices that do not completely comply with the POE standard. As described above, since the characteristics of various power receiving devices are different, especially the combination result of different resistance characteristics and different capacitance characteristics, changes the characteristics of whether the device is suitable for receiving power from the power supply equipment, and it is still difficult to achieve an accurate detection result by simply detecting the resistance characteristics and capacitance characteristics of the device under test.
Ideally, the external devices connected to the specific ports 11, 12, 14 are all powered devices conforming to the IEEE POE standard and powered devices compatible with the standard. During the testing phase, these external devices are all called "dut". A powered device that is detected to be compliant with the IEEE POE standard and a powered device that is compatible with the standard may be referred to as a "powered device".
Fig. 2 is a voltage-time and current-time comparison diagram showing the relationship between the detection voltage signal applied to the connection port and the response signal detected from the connection port according to the power receiving device detection method of the power over ethernet system of the present invention when the device connected to the connection port is a standard or compatible power receiving device in the power over ethernet system. The dut in the figure exhibits a capacitance value of 0.1uF in accordance with the IEEE standard.
The invention provides a novel detection method for a powered device of an Ethernet power supply system. The method is applied to a powered device detection device of a power over ethernet system shown in fig. 1, and includes the following steps when the powered device detection is performed on a device to be detected connected with a communication port:
applying a detection voltage signal to the communication port, wherein the detection voltage signal sequentially comprises a first voltage V1, a second voltage V2, a third voltage V3 and a fourth voltage V4; and
a first current value I1 is measured from the communication port a predetermined time after the first voltage is applied, a second current value I2 is measured from the communication port a predetermined time after the second voltage is applied, a third current value I3 is measured from the communication port a predetermined time after the third voltage is applied, and a fourth current value I4 is measured from the communication port a predetermined time after the fourth voltage is applied.
In the example shown in the figure, the first and third voltages have substantially the same value, and the second and fourth voltages have substantially the same value. In this embodiment, V1 ═ V3 ═ 8V, and V2 ═ V4 ═ 4V. However, other levels of voltage may be suitable for use in the present invention. In addition, the fourth voltage is applied for a longer time than the second voltage. In a preferred embodiment of the present invention, the fourth voltage is applied for 1.2 to 2.5 times, more preferably 1.5 to 2.0 times the second voltage. That is, the application time of the fourth voltage is the sum of the second voltage application time and the extension time; the extension time is 0.2 to 1.5 times, preferably 0.5 to 1.0 times the second voltage application time. In this embodiment, the second voltage application time is 72ms, and the fourth voltage application time is 108 ms. In addition, the application time of the first voltage and the third voltage are both 72 ms. The prolonged voltage application time is helpful for enabling the voltage applied to the device to be tested to reach a stable state, and providing correct measurement results and comparison information.
As shown in the figure, the capacitance value of the DUT is 0.1 uF. The voltage V0 applied to the connection port by the detection device 10 during initialization is 0V. After the testing device 10 starts to apply a current limit (800uA) of-8V to the connection port at time T1, the voltage applied to the device under test reaches the predetermined-8V within a short time, e.g., 4ms, after time T1. The detection device 10 can detect the current value of I1 in the vicinity of time T2. When the testing device 10 applies a voltage of-4V to the connection port at time T2, the voltage applied to the device under test reaches a predetermined voltage of-4V at time T2. The detection device 10 can detect the current value of I2 in the vicinity of time T3. Similarly, when the testing device 10 applies a voltage of-8V to the port at time T3, the voltage applied to the device under test reaches the predetermined voltage of-8V at time T3. The detection device 10 can detect the current value of I3 in the vicinity of time T3. When the testing device 10 applies a voltage of-4V to the connection port at time T4, the voltage applied to the device under test reaches a predetermined voltage of-4V at time T4. The detection device 10 can detect the current value of I4 in the vicinity of time T5.
In this case, the detection apparatus 10 can obtain the values of Rdet1 and Rdet2 by calculating Rdet1 ═ V1-V2)/(I1-I2) and Rdet2 ═ V3-V4)/(I3-I4. In theory Rdet1 ═ Rdet 2. The inspection device 10 can determine whether to perform the next step of "classifying" the dut connected to the connection port according to the values of Rdet1 and Rdet2 by known methods. And according to the classification result, supplying corresponding power to the connection port.
If the external devices 21, 22, 23 connected to the ports 11, 12, 13, 14 do not conform to the POE standard of IEEE, including the resistive and/or capacitive characteristics, the test procedure described above cannot produce the result shown in FIG. 2.
Fig. 3 is another voltage-time and current-time comparison graph showing the relationship between the detection voltage signal applied to the connection port and the response signal detected from the connection port by the detection method of fig. 2 when the device connected to the connection port is a device unsuitable for power supply in the power over ethernet system.
In the case of fig. 3, the device connected to the connection port exhibits a resistance value of 32K ohms, which is outside the range specified by the POE standard of the IEEE. And the device exhibits a high capacitance of 10 uF. The results of the test performed on the device by the test method of the present invention are shown in FIG. 3. Wherein, the upper part is the actual voltage value measured at the connection port after-8V, -4V, -8V and-4V test voltage is applied to the connection port connected with the device to be tested in sequence. Below is the value of the response signal current of the DUT measured at the connection port after, for example, 70ms after each test voltage is applied.
As shown in the figure, when the power equipment detection device 10 detects the powered device of the device, the first voltage V1 is applied to a specific connection port, then the second voltage V2 is applied, and the current value of the response signal is measured after a certain time from the application of the respective voltages. For example, the initial voltage V0 at time T0 is 0V, the first voltage V1 at time T1 is-8V, and the second voltage V2 at time T2 is-4V. But the charging speed is slow because the capacitance of the device to be tested is as high as 10 uF. At about time T2, only a voltage of-5V is energized at the port. During the voltage ramp up to-4V, the capacitor has sufficient time to discharge, so that at time T3, a voltage of-4V is available at the port. At this time, the current measured at the connection port is 800uA of I1 current around time T2 and 125uA of I2 current around time T3.
This phenomenon indicates that the device connected to the connection port is a device that does not comply with the POE standard of IEEE. Due to the capacitance value exhibited being too high, the measured current value approaches the initial current limit value of 800uA after application of the first voltage V1.
Fig. 4 is another voltage versus time and current versus time graph showing the relationship between the application of a detection voltage signal to a connection port and a response signal detected from the connection port by the detection method of fig. 2 when a device connected to the connection port is another device unsuitable for power supply in a power over ethernet system.
In the case of fig. 4, the device connected to the connection port exhibits a resistance characteristic of 32K ohms, which is outside the range specified by the POE standard of the IEEE. And the device also exhibited a higher capacitance of 5.15 uF. As shown in the figure, the voltage signal applied by the detection device 10 of the power equipment to the connection port connected with the device is 0V at the initial voltage V0 at the time T0, is-8V at the time T1 when the first voltage V1 is applied to the connection port, and is-4V at the time T2 when the second voltage V2 is applied. The capacitance of the dut is not as high as the embodiment of fig. 3, but is as high as 5.15uF, resulting in slow charging speed. As a result, at time T2, a voltage of-8V may be measured at the port, but the capacitor does not have sufficient time to discharge during the voltage ramp to-4V, so at time T3, a voltage of less than-4V, such as-5V (top of FIG. 4), may be measured at the port. At this time, the current measured at the port may be 250uA of I1 near time T2, but close to 0uA of I2 near time T3 (below FIG. 4).
This phenomenon indicates that the device connected to the connection port is a powered device that does not comply with the IEEE POE standard. Due to the capacitance value exhibited being too high, the measured current value after application of the second voltage V2 is close to 0.
Fig. 5 is another voltage versus time and current versus time graph showing the relationship between the detection voltage signal applied to the connection port and the response signal detected from the connection port by the detection method of fig. 2 when the device connected to the connection port is another device unsuitable for receiving power in a power over ethernet system.
In the case of fig. 5, the device connected to the connection port exhibits a resistance characteristic of 32K ohms, also exceeding the range specified by the POE standard of the IEEE. And the device also exhibited a slightly higher capacitance of 3.5 uF. The detection device 10 of the power supply apparatus applies a voltage to a connection port to which the device is connected, an initial voltage V0 is 0V at time T0, a first voltage V1 is-8V at time T1 is applied to the connection port, and a second voltage V2 is-4V at time T2. The capacitance of the dut is not as high as in the examples of fig. 3 and 4 and is close to the range specified by the POE standard of IEEE. Therefore, when a known detection device is used for detection, the device is determined to be a power receiving device conforming to the POE standard of IEEE or a power receiving device compatible with the standard by mistake.
In detail, as a result of the detection voltage signal sent from the detection device 10 to the connection port connected to the device under the condition shown in FIG. 5, a voltage of-8V may be measured at the connection port at time T2, and a voltage of-4V may also be measured at time T3. At this time, the current value measured at the port may be 250uA of I1 near time T2, and any I2 current value between 0 and 125uA near time T3. This is because the capacitance of the dut is slightly higher than the standard range and charging may still be completed during the test period after voltage conversion. Since the current value measured at T3 may be within the set range of the detection device, the detection of the dut may be determined according to the measurement result, as measured by a conventional device. However, since the capacitance of the dut is as high as 3.5uF, the dut has not stabilized at time T3, and the value of I2 is not the correct current value. The result of the determination based on the value of I2 is, of course, an error.
To solve the problem, the powered device detecting apparatus of the power over ethernet system of the present invention further applies a third voltage V3 and a fourth voltage V4 to the connection port. The third voltage V3 has the same value as the first voltage V1; the fourth voltage V2 has the same value as the second voltage V2. For example, V1 ═ V3 ═ -8V, V2 ═ V4 ═ -4V. However, the applying time of the fourth voltage V4 is longer than the applying time of the second voltage V2, so that the value of the fourth voltage is stabilized. For example, the application time of the first voltage, the second voltage, and the third voltage is 72ms, but the application time of the fourth voltage is 108 ms. As shown in FIG. 5, when the detecting device applies a voltage of-8V to the port at time T3, a voltage of-8V can be measured at the port after time T3. When the detecting device applies a voltage of-4V to the port at time T4, a voltage of-4V is not measured at the port until a considerable period of time after time T4, for example, a time longer than 72 ms.
According to the design of the present invention, after the third and fourth voltage signals are sent out by the detection device, 250uA of current can be measured at the connection port near time T4, and 125uA of current can be measured at the connection port near time T5. Thereby obtaining a correct detection result.
Therefore, under the conditions shown in fig. 5, the Rdet value calculated according to I1, I2 (Rdet1 ═ V1-V2)/(I1-I2)) would be much smaller than the Rdet value calculated according to I3, I4 (Rdet2 ═ V3-V4)/(I3-I4)). At the very least, there is a significant difference between the two. Therefore, the device under test connected to the connection port can be determined from the difference value between the two values, and is still not a powered device meeting the POE standard of IEEE.
According to the above analysis results, the power receiving device detection device 10 of the power over ethernet system of the present invention provides a detection operation unit 15 for controlling the voltage signals applied to the connection ports 11, 12, 13, 14, and determining whether the external device connected to the connection port is a power receiving device meeting the POE standard of IEEE or a power receiving device compatible with the standard according to the response current value measured at any one of the connection ports 11, 12, 13, 14. The detection device 10 is provided with: a voltage supplier 16 for supplying a voltage signal of a constant current to the specific connection ports 11, 12, 13, 14; a current detector 17 for detecting the current value at the specific connection port 11, 12, 13, 14.
The detection device 10 of the present invention is configured to: a detection voltage signal may be applied to the communication port, the detection voltage signal including, in order, a first voltage V1, a second voltage V2, a third voltage V3, and a fourth voltage V4. The first voltage and the third voltage have substantially the same value, and the second voltage and the fourth voltage have substantially the same value. The application time of the fourth voltage is the sum of the application time and the extension time of the second voltage. The extension time is 0.2 to 1.5 times, preferably 0.5 to 1.0 times the second voltage application time.
The detection device 10 is further configured to:
a first current value I1 measured from the communication port a predetermined time after the first voltage is applied, a second current value I2 measured from the communication port a predetermined time after the second voltage is applied, a third current value I3 measured from the communication port a predetermined time after the third voltage is applied, and a fourth current value I4 measured from the communication port a predetermined time after the fourth voltage is applied;
values were calculated for Rdet1 ═ V1-V2)/(I1-I2) and Rdet2 ═ V3-V4)/(I3-I4,
when one of the current values I1, I2, I3 and I4 exceeds a first predetermined value range, determining that the communication port is not connected with a power receiving device suitable for power supply;
when the delta Rdet is larger than a second preset value Rdet1-Rdet2, judging that the communication port is not connected with a power receiving device suitable for power supply; otherwise, the communication port is judged to be connected with the power receiving device suitable for power supply.
In a preferred embodiment of the invention, the first predetermined range of values may be set generally between 0.02mA and 0.78mA, preferably between 0.04mA and 0.76 mA. The second predetermined value may be set generally between-1000 and 1000, preferably between-500 and 500.
According to the above description, the power-supplied device detection method of the power over ethernet system of the present invention is a method performed in the power supply apparatus of the power over ethernet system. The power supply equipment is provided with at least one communication port and a detection device, wherein the communication port can be connected with a power receiving device through a network cable, and the detection device is connected with the communication port.
Fig. 6 is a flowchart illustrating a power receiving device detection method of the power over ethernet system according to an embodiment of the present invention. As shown in the figure, the method for detecting a powered device in a power over ethernet system according to the present invention includes the following steps:
in step 601, applying a detection voltage signal to the communication port by the detection device, wherein the detection voltage signal comprises a first voltage V1, a second voltage V2, a third voltage V3 and a fourth voltage V4 in sequence;
in the detection voltage signal, the first voltage and the third voltage have substantially the same value, and the second voltage and the fourth voltage have substantially the same value. The application time of the fourth voltage is the sum of the application time and the extension time of the second voltage; the extension time is 0.2 to 1.5 times, preferably 0.5 to 1.0 times the second voltage application time.
In step 602, the detecting device measures a first current value I1 from the communication port a predetermined time after the first voltage is applied, measures a second current value I2 from the communication port a predetermined time after the second voltage is applied, measures a third current value I3 from the communication port a predetermined time after the third voltage is applied, and measures a fourth current value I4 from the communication port a predetermined time after the fourth voltage is applied. Thereafter, in step 603, the detection apparatus calculates values of Rdet1 ═ V1-V2)/(I1-I2) and Rdet2 ═ V3-V4)/(I3-I4. Next, in step 604, the detecting device determines whether one of the current values I1, I2, I3, I4 exceeds a first predetermined value range. If yes, in step 605, it is determined that the communication port is not connected to a power receiving device suitable for power supply. If not, the process jumps to 606. In step 606, the detection device 10 determines whether Δ Rdet — Rdet1-Rdet2 is greater than a second predetermined value. If yes, in step 607, it is determined that the communication port is not connected to a power receiving device suitable for power supply; otherwise, in step 608, it is determined that the communication port is connected to a powered device suitable for power supply.
As previously mentioned, in the preferred embodiment of the present invention, the first predetermined range of values may be set generally between 0.02mA and 0.78mA, preferably between 0.04mA and 0.76 mA. The second predetermined value may be set generally between-1000 and 1000, preferably between-500 and 500.
As described above, the present invention provides a novel power receiving device detection apparatus and method for a power over ethernet system, which only requires a single detection period to correctly exclude external devices unsuitable for power supply and obtain a correct value of Rdet.
In the above embodiment, the detecting device 10 applies a voltage signal to the connection port to be tested, and measures a response current value after a certain time. However, it is known to those skilled in the art that the current signal is applied to the connection port to be tested, and the response voltage value is measured after a certain time, so that the corresponding resistance value can still be calculated accordingly. In addition, in the above embodiments, the first voltage and the third voltage are signals with levels higher than the second voltage and the fourth voltage. However, in application, the first voltage and the third voltage may be lower than the second voltage and the fourth voltage.
The above is a description of embodiments of a power receiving device detection apparatus and method for a power over ethernet system according to the present invention. It will be appreciated by those skilled in the art that the embodiments of the invention may be practiced with modification of the disclosed embodiments, which are related to the known technology, and which may have similar or identical effects. Accordingly, such modifications are intended to be within the scope of this invention.
Claims (14)
1. The detection device is used for being arranged in power supply equipment of the power over Ethernet system, the power supply equipment is provided with at least one communication port, and the communication port can be used for connecting the power receiving device through a network cable; the detection device is connected to the communication port and is configured to:
applying a detection voltage signal to the communication port, wherein the detection voltage signal sequentially comprises a first voltage V1, a second voltage V2, a third voltage V3 and a fourth voltage V4; wherein, the first voltage and the third voltage have the same value, and the second voltage and the fourth voltage have the same value; the application time of the fourth voltage is the sum of the application time and the extension time of the second voltage;
the detection device is further configured to:
a first current value I1 measured from the communication port a predetermined time after the first voltage is applied, a second current value I2 measured from the communication port a predetermined time after the second voltage is applied, a third current value I3 measured from the communication port a predetermined time after the third voltage is applied, a fourth current value I4 measured from the communication port a predetermined time after the fourth voltage is applied;
values were calculated for Rdet1 ═ V1-V2)/(I1-I2) and Rdet2 ═ V3-V4)/(I3-I4,
when one of the current values I1, I2, I3 and I4 exceeds a first preset value range, judging that the communication port is not connected with a power receiving device suitable for power supply; and is
When the delta Rdet is larger than a second preset value, Rdet1-Rdet2, judging that the communication port is not connected with a power receiving device suitable for power supply; otherwise, the communication port is judged to be connected with a power receiving device suitable for power supply.
2. The powered device detection apparatus of a power over Ethernet system of claim 1,
the extension time is 0.2 to 1.5 times the second voltage application time.
3. The powered device detection apparatus of a power over Ethernet system of claim 2,
the extension time is 0.5-1.0 times of the second voltage application time.
4. The powered device detection apparatus of a power over Ethernet system of claim 1,
the current limiting signal with-8V voltage is set to have an upper current value limit of 0.0008A, the current limiting signal with-4V voltage is set to have an upper current value limit of 0.0008A, and the first preset value range is set to be between 0.00002A and 0.00078A.
5. The powered device detection apparatus of a power over Ethernet system of claim 4,
the first predetermined range of values is set between 0.00004A and 0.00076A.
6. The powered device detection apparatus of a power over Ethernet system of claim 1,
the units of V1, V2, V3, V4 are V, and the units of I1, I2, I3, I4 are A,
the first and the third current limiting signals with-8V voltage have an upper current value limit of 0.0008A, the second and the fourth current limiting signals with-4V voltage have an upper current value limit of 0.0008A, and the second preset value is set to be between-1000 and 1000.
7. The powered device detection apparatus of a power over Ethernet system of claim 6,
the second predetermined value is set to be between-500 and 500.
8. A detection method for a powered device of a power over Ethernet system is characterized in that the detection device is executed in power equipment of the power over Ethernet system; the power supply equipment is provided with at least one communication port and a detection device, the communication port can be connected with a power receiving device through a network cable, and the detection device is connected with the communication port; the method is used for detecting the characteristics of a power receiving device connected to the communication port and comprises the following steps:
applying a detection voltage signal to the communication port, wherein the detection voltage signal sequentially comprises a first voltage V1, a second voltage V2, a third voltage V3 and a fourth voltage V4;
wherein, the first voltage and the third voltage have the same value, and the second voltage and the fourth voltage have the same value; the application time of the fourth voltage is the sum of the application time and the extension time of the second voltage;
a first current value I1 measured from the communication port a predetermined time after the first voltage is applied, a second current value I2 measured from the communication port a predetermined time after the second voltage is applied, a third current value I3 measured from the communication port a predetermined time after the third voltage is applied, a fourth current value I4 measured from the communication port a predetermined time after the fourth voltage is applied;
values were calculated for Rdet1 ═ V1-V2)/(I1-I2) and Rdet2 ═ V3-V4)/(I3-I4,
when one of the current values I1, I2, I3 and I4 exceeds a first preset value range, judging that the communication port is not connected with a power receiving device suitable for power supply;
when the delta Rdet is larger than a second preset value, Rdet1-Rdet2, judging that the communication port is not connected with a power receiving device suitable for power supply; otherwise, the communication port is judged to be connected with a power receiving device suitable for power supply.
9. The powered device detection method of a power over Ethernet system of claim 8,
the extension time is 0.2 to 1.5 times the second voltage application time.
10. The powered device detection method of a power over Ethernet system of claim 9,
the extension time is 0.5-1.0 times of the second voltage application time.
11. The powered device detection method of a power over Ethernet system of claim 8,
the current limiting signal with-8V voltage is set to have an upper current value limit of 0.0008A, the current limiting signal with-4V voltage is set to have an upper current value limit of 0.0008A, and the first preset value range is set to be between 0.00002A and 0.00078A.
12. The power over Ethernet system powered device detection method of claim 11,
the first predetermined range of values is set between 0.00004A and 0.00076A.
13. The powered device detection method of a power over Ethernet system of claim 8,
the units of V1, V2, V3, V4 are V, and the units of I1, I2, I3, I4 are A,
the first and the third current limiting signals with-8V voltage have an upper current value limit of 0.0008A, the second and the fourth current limiting signals with-4V voltage have an upper current value limit of 0.0008A, and the second preset value is set to be between-1000 and 1000.
14. The power over Ethernet system powered device detection method of claim 13,
the second predetermined value is set to be between-500 and 500.
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| TW104138946A TWI584611B (en) | 2015-11-24 | 2015-11-24 | Inspection device and method for powered devices in a Power over Ethernet system |
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| CN108181543A (en) * | 2017-11-30 | 2018-06-19 | 国网河南省电力公司偃师市供电公司 | The power receiving device detection device and method of a kind of Power over Ethernet system |
| CN112684383A (en) * | 2020-11-18 | 2021-04-20 | 杭州士兰微电子股份有限公司 | Load connection detection method in Ethernet power supply system and power supply device |
| TWI768617B (en) * | 2020-12-24 | 2022-06-21 | 九暘電子股份有限公司 | Power over ethernet system having multiple power source devices and control device thereof |
| CN113125877B (en) * | 2021-03-02 | 2022-12-06 | 华为技术有限公司 | PD detection equipment for powered device |
| CN113777424B (en) * | 2021-08-24 | 2024-03-29 | 上海超丰科技有限公司 | Method for detecting power receiving connection in Ethernet power supply system and power supply device |
| CN113777425B (en) * | 2021-08-24 | 2024-03-29 | 上海超丰科技有限公司 | Hierarchical detection method of power over Ethernet system and power supply equipment |
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| US10142116B2 (en) | 2018-11-27 |
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